I saw in docus: to identify which column is updted in the "after update of col1, col2,.... on table t" database trigger, you can use:
IF updating('col1') then
do_1
ELSIF updating('col2') then
do_others
end if;

Is this true? Or we have to use:
If :new.col1 <> :0ld.col1 OR (:new.col1 is null and :0ld.....).